Piston expander



March 1937. D. M. soLEN ERGR 9 I PISTON EXPANDER] Filed Nov. 4, 1955 2 Sheets-Sheet l 3nventor Df/M/ MS'OZf/VBERGEE attorneys March 9, 1937.

0.. SOLENBERGER 2,Q73,49 9

' PISTON EXPANDER Filed Nov. 4, 1935 2 Sheets-Sheet 2 3nven tor DfA/V M saith/B51965)? 45 (Ittomegs Patented Mar. 9, 1937 UNITED STATES PATENT OFFICE PISTON EXPANDER of Ohio Application November 4,

3 Claims.

This invention relates to piston skirt expanding devices and more particularly to an improved universal spring ring type piston expander which may be readily installed in substantially all types 5 of pistons.

A large number of different types of devices have been made and used for expanding the skirts of split skirt pistons of the type commonly used in modern internal combustion engines.

Such expanding devices may be used either to size or shape the skirt of a new piston or to resize the skirt of a piston after it has become undersize in use due to collapse of the skirt walls or to wear. One of the most difficult problems to overcome in making a piston skirt expander of this type is to provide means for holding the expander in the piston. In an engine operating between 3000 R. P. M. and 4000 R. P. M. the inertia forces acting to dislodge the expander are very great and it is thus important to reduce the weight of the expander to the lowest possible value while giving the desired expanding force. Multi-piece expanders of various styles have been proposed but difliculty has been experienced with many of these because the pieces, no matter how well secured to each other, tend to become separated, dropping into the crank case and permitting the piston to resume its previous undersized condition.

Another problem of great importance is the provision of a universal piston expanding device which may be used in substantially all of the large number of difierent types of present day internal combustion engine pistons. These have a variety of different skirt arrangements and the interior contour varies greatly. To satisfactorily solve the problem of providing an expander which will require a minimum inventory on the part of the engine repair shop, the expander should be 40 adapted to be inserted in substantially all types of pistons. Further it should be possible to obtain different degrees of expansion of any given piston.

I am aware that a considerable number of ring 4:, type piston expanders have been proposed and used. These ring type expanders have been made of round, rectangular and other cross .sections and are generally formed out of spring steel wire. Some have been substantially circular in form so while others have been corrugated in various ways and adapted to fit in the ledges and orifices which exist in the interior of the piston. Ring type pis ton expanders made of round or rectangular cross section wire have been made to fit in grooves 55 which are cut by a suitable tool in the inside of 1935, Serial No. 48,219

the piston skirt. None of these previously proposed ring type expanders, with which I am familiar, have, however, been universally adaptable to all types of pistons nor have they been suitable for thin skirt pistons. All of them, so far as 5 I am aware, which are not provided with special retaining means, necessitate cutting a relatively wide and/or deep groove in the inside or the piston skirt in order to provide an annular recess to hold the expander in the piston during oper- 1o ation. In order to obtain the necessary expansive force a round wire ring expander must be of such diameter that, in order to properly and securely install the expander in a piston, a groove must be cut in the inner wall of the piston. skirt of 15 such depth and radius as to seriously weaken the thin skirt pistons now in use. Moreover, in many pistons the finished portion of the inner wall of the piston skirt (referred to more fully below) is not sufiiciently wide to permit the cutting of 20 the necessarily relatively wide and deep groove which must be provided in order to hold the previously proposed round or rectangular cross sectioned ring expanders securely in the piston.

It is therefore an object of my invention to provide a piston expander or resizing device, of minimum weight for a given expanding force, which will be securely held in the piston at all times without harmful vibration. Other objects of my invention are: the provision of a piston expander which may be easily installed in and removed from substantially all of the different designs and types of pistons now in use; the provision of a piston expander which is supported at all points whereby vibration and consequent fatigue failure is eliminated; the provision of a piston expander which is readily susceptible to extremely accurate, uniform and economical manufacture; the provision of a piston expander, the expansive force of which may be readily determined and maintained constant during the manufacturing processes; the provision of a series of pistonexpanders of successively larger sizes whereby the desired degree of expansion may be given to any piston; the provision of a piston skirt expander which is of simple form and in which the metal forming the spring member is not subjected to sharp bends or stresses during the manufacturing process and therefore has the maximum strength for its weight; the provision of a piston expander which will not destroy the balance of the piston in which it is installed, and the provision of improved tools for use during installation and removal of my expander from the piston.

In order to fulfill the above noted objects I provide a piston skirt expander constituting a ring of suitable spring steel or the like. This ring is provided, on its outer periphery, with an outwardly extending ridge or flange of relatively small cross sectional area, which flange is adapted to fit into a corresponding relatively small groove which is out or otherwise formed in the inside of the piston skirt. The great majority of pistons which are used in internal combustion engines have a finished portion on the inside of the skirt adjacent the bottom thereof. This portion may be of varying widths in different types of pistons ranging from perhaps e g to A" or more. Generally, the function of this finished ring on the inside of the piston skirt is to provide an accurate surface for centering the piston when finishing the outside of the piston during manufacture. In all pistons of a given type and size this finished ring on the inside of the bottom of the skirt will be of substantially the same diameter. I prefer to install my improved expanding device in a groove formed in this finished ring portion of the piston skirt expander as thus I can provide an expander which will fit all individual pistons of any particular type and size and exert a substantially uniform expanding force on all.

The above and other objects of my invention will appear from the following description of several embodiments thereof, reference being had to the accompanying drawings illustrating my improved expander and several types of installation tools, and in which- Figure 1 is a side elevation, approximately full scale, of a split skirt piston with the bottom portion of the skirt in section and illustrating one of my improved ring type expanders installed in the piston skirt.

Figure 2 is a horizontal cross sectional View taken on line 22 of the piston illustrated in Figure 1, one end of the expander being shown in full view for purposes of better illustration.

Figure 3 is an enlarged cross sectional view taken substantially on line 33 of Figure 1 and illustrating one embodiment of my ring expander installed in one type of piston.

Figure 4 is a view generally similar to Figure 3 but illustrating a slightly modified form of expander installed in a piston having a thin walled skirt.

Figures 5, 6, 7 and 8 are views generally similar to Figures 3 and 4 but illustrating various modifications of my expander installed in pistons having various types of skirt walls and various forms of finished surface on the interior of the skirt wall.

Figure 9 is a fragmentary horizontal cross sectional view of one of my rings, the section being taken through the installation tool slot.

Figure 10 is a view similar to Figure 9 but illustrating a modified form of hole extending through the expander ring for accommodating the installation tools.

Figure 11 is an illustrative View of a piston, partly in vertical cross section, and a preferred form of grooving tool for cutting the groove in the inner surface of the piston skirt.

Figure 12 is a view of one type of installation tool showing the tool in position to collapse the expander.

Figure 13 is a side elevation of the gripping tool of Figure 12.

Figure 14 is a side elevation generally similar to Figure 13 but showing pins on the ends of the tool arms adapted to engage the type of aperture illustrated in Figure 10.

Figure 15 is a plan view illustrating a piston skirt, one of my expanders in position to be inserted in the piston skirt, and an installation tool which is adapted to collapse the expander ring and hold it in collapsed position while it is inserted in the piston.

Figure 16 is a side elevation of the installation tool shown in Figure 15.

Referring now to Figures 1 and 2, the piston illustrated is of a standard type and includes a head portion l and a skirt portion 2 which is split from the bottom to the top edge thereof at 3. In the particular piston illustrated an internal annular flange 4 is provided adjacent the bottom of the piston slL'rt. The inner surface of this flange is finished to a standard dimension and this surface is used to provide an accurate centering surface during the finishing of the outside of the piston skirt. A small groove 5, preferably about deep and 3 2" wide, has been formed in the flange 4 of the piston skirt. In this groove 5 is seated the flange 6 of my ring expander 1 which is of generally round cross section, its outer periphery being flattened and provided with the radially outwardly projecting annular flange 6. tially by in cross section and is adapted to fit freely in the groove 5 in the piston skirt. Slots II and 12 are cut adjacent the spaced ends 9 and I!) of the expander. As seen in Figure 1 these slots lie just below the flange 5 so that the flange is continuous throughout the entire circumference of the ring. If desired, however, the slots H and I2 might be cut through the ring on the same plane as the flange 5. As is best seen in Figure 9, these slots I l and I2 may be conveniently cut by a milling cutter of proper diameter (indicated at l3 in dot and dash lines on Figure 9). In this way the end of the slot nearest the end of the expander forms a hook which may be readily engaged by a suitable installation tool. The angle of the ends of the slots II and I2 makes possible the collapse of the expander for installation purposes without danger of its slipping off the gripping fingers of the installation tool. As shown in Figure 10 a hole may be drilled through the expander at a suitable'angle to give the same hook effect. By slotting the expander, as shown at I l and l 2, a thin tool can be used and the resiliency and strength of the expander ring will not be seriously impaired.

In Figures 1 and 2 the flange 6 of the expander 1 is disposed midway between the top and bottom of the ring and the slots I l and I2 extend through the body of the expander just below the flange. In Figures 3 and 4 the flange of the expander is disposed just above the center of the cross section of the expander and the slot just below. This latter arrangement is preferred although the arrangement of Figures 1 and 2 or other locations of the slots and flange may in some instances be desirable. V

In the enlarged views, Figures 3 to 8 inclusive, various common types of piston skirts are illustrated with several different embodiments of my expander. In Figure 3 the bottom of the skirt I5 is provided with a flange l6 grooved at IT to ac commodate the expander. In Figure 4 a piston having a thin walled skirt I8 is illustrated and in Figure 5 a piston having a skirt l9 with a finished portion 20 at the bottom thereof of reduced thickness. In this figure the expander 2| is made from substantially square stock having a flange 22 on its center line and a slot 23 just below the flange. In the embodiment shown in Figure 6 This flange is also substan-- To cut the groove,

the flange is even with the top surface of the expander and the slot is approximately midway of the vertical dimensions of the expander. Figure '7 illustrates an expander made of rectangular stock arranged diagonally with the retaining flange formed on one corner thereof. The piston skirt 24 illustrated in this view is provided with a very small annular'fiange or ridge 25 on its inner surface. In actual practice the flange 25 in pistons of this type may have a vertical'dimension of only about 33 and the thickness of the skirt may be less than This illustrates the advantage of my small flange arrangement which can be installed in pistons where it would be impossible to cut a groove large enough to properly support either a rectangular or round cross sectional expander ring of sufficient size to exert the required force.

Figure 8 illustrates still another modification of my expander ring installed in a piston and it will various cross sectional forms may be adapted for my expander provided a suitable retaining fiange is formed thereon and suitable means are provided for collapsing the ring for installation and removal.

In order to cut a proper groove in the skirt of the piston to accommodate the retaining flange of my expander I prefer to use a small milling cutter M (see Fig. 11) which is provided with cutting teeth 21 mounted on a shaft 28; The depth of the groove cut by this cutter is determined by the shoulder 29 and the shaft 28 may be conveniently gripped in the chuck 3B of a drill press. the piston P is placed on the base 3| with the skirt end up and the chuck 30 is adjusted so that the teeth 21. will be at the proper height to cut the groove 32 in the inside finished portion 33 of the piston skirt. The piston P may be conveniently manipulated by hand to cause the milling cutter to cut the groove around the entire circumference of the piston.

In order to facilitate installation of my expander in a piston in which a suitable groove has 7 been cut, I have provided the installation tool illustrated in Figures 12 and 13. This consists essentially of a pair of levers 34 and 35 pivoted at 36 and having their short ends bent downwardly and tapered as indicated at 31 and 38 so that they will fit into the slots H and I2 of the ring 1. When the lever arms 34 and 35 are gripped and squeezed together the ends 31 and 38 will engage the undercut ends of the slot H and I2 and the ring willbe collapsed. As the ends 31 and 38 are Offset from the arms 34 and 35, as is clearly seen in Figure 13, the expander may be readily dropped into position in the end of the piston skirt.

Figure 14 illustrates a device which is the same as that shown in Figures 12 and 13 except that pins 39 are provided in place of the thin ends 31 and 38. These pins are adapted to enter holes 40 (see Fig. in the ends of the expander.

The installation tool illustrated in Figures and 16 consists of a threaded rod 42 having a pin 43 extended therethrough to facilitate turning to collapse the ring. The threaded rod 42 extends through a threaded aperture in the sliding member 44 and is rotatably supported at its ends in the fixed member 45. A guide rod 46 extends through the sliding member 44 and is supported by the member 45 at 41. The sliding member 44 will be moved toward or away from the fixed member 45 upon rotation of the threaded rod 42. J-Iooks 48 and 49 are secured to the lower ends of the sliding member 44 and fixed member 45 respectively. These hooks are adapted to engage the slots at the ends of the expander as is clearly seeninFi'gure l5 and, by turning the screw 42, they may be drawn together to collapse the expander 1 so that it may be dropped into position in the piston skirt. "This device possesses the advantage that the expander may be maintained in any degree of contraction by suitable adjustment of the threaded. rod 42 and insertion of the flange of the expander in the groove in the piston skirt is thereby facilitated.

By providing a ring type piston expander with a relatively small outwardly extending annular flange around is entire circumference, which flange need be only approximately g high by g" wide for all types of pistons used inmodern automotive vehicles, I have produced an expander having low weight for a desired expanding force which expander is secured with the necessary rigidity in the piston skirt and is supported at all points in its circumference thus effectively preventing vibration and resulting failure. The shallow and narrow groove which is-necessary to accommodate the small flange on the expander can be cut in substantially all present day types of pistons and therefore my expander is universally adaptable.

I prefer to make my expanders of round cross section wire by forming annealed spring steel wire into rings of accurate diameter. The method and apparatus disclosed in my co-pending United States application, Serial No. 15,356, filed April 8, 1935, may be advantageously used for forming the expanders. After round wirev which can be maintained within very close; limits of diameter, is bent into the desired ring form, a plurality of rings may be placed on a suitable arbor and the retaining flange turned on the outer surface thereof. The rings may then be slotted to accommodate the installation tool and tempered.

I contemplate the manufacture of a series of expander rings varying in diameter by small in crements, for example Each size expander may readily be held to certain standards in order to provide a predetermined amount of open ing for the piston skirt of any given type of piston. In use, if one size expander does not give quite enough expansion ton to the cylinder in which it is to be used, the next larger size may be installed. In this way substantially all pistons may be given the desired degree of expansion and brought to the proper diameter and the shop doing the work need keep on hand only a supply of expanders covering the range of sizes of pistons used. The expanders for practically all types of pistons are the same and the same installation tool can be used for cutting the groove andinserting the expanders in practically all types of pistons.

I havefound that by using the series of expanders in sizes which increase by in diam eter I can expand theusual split skirt piston as little as .001 or as much as .015" or more. My expander permits the expanded piston to contract and expand in a cylinder as the piston moves up and down therein thus maintaining the desired wall contact and retaining the advantages obtained by the slotted skirt construction. My expander may be disposed in the cylinder with the ends of the expander on either side of the piston skirt slot or they may be arranged with the gap between the expander ends at any other desired position around the inner circumference to properly fit the pisof the piston skirt. Due to the fact that when a circular spring such as my expander is contracted it no longer remains in circular form I am able to use my expanders to force the skirts of pistons slightly out of round. This is considered desirable in some instances as is evidenced by the fact that pistons are now commonly cam ground so that they are not round but rather of oval cross sectional shape. My expanders can be used to force the skirt of an unslotted piston out of round and I have found that by inserting my expander in grooves in the skirts of unslotted heavy cast iron pistons the skirts may be forced and held out of round .005" or more and in fairly light unslotted skirt pistons my expanders may be used to throw the piston skirt out of round as much as .015".

In installing my expander in a piston I prefer to make the groove in which the retaining flange is disposed slightly deeper than the flange so that the body of the expander engages directly on the piston skirt walls and the narrow retaining flange serves only to hold the expander in position in the skirt.

Although I have described the illustrated embodiments of my invention in considerable detail it will be understood by those skilled in the art that various modifications can be made in the expander and installation equipment herein illustrated and described without departing from the spirit of my invention. I do not therefore wish to be limited to the specific forms herein described but claim as my invention all embodiments thereof coming within the scope of the appended claims.

I claim: 1. In combination with a piston having a skirt portion, the inner circumference of said skirt portion being grooved, a skirt expander comprising a circular spring ring body having suflicient mass to exert a predetermined expanding force upon being collapsed a predetermined amount and having a circumferentially extending inte grally formed retaining flange projecting from the outer periphery of said body, the mass of said flange being small as compared to the mass of the ring body, and the groove in the piston skirt being of such dimensions that only said retaining flange of said expander is disposed in said groove in the piston skirt.

2. In combination, a piston having a skirt, said skirt being grooved circumferentially of its inner surface, the radial cross sectional dimensions of said groove being approximately inch by inch, and a. split spring steel ring body having an integral flange on its outer periphery fitting said groove in the piston skirt and holding said spring ring body in position in the piston.

3. In combination, a piston having a skirt, said skirt being grooved circumferentially of its inner surface, and a split spring ring body having a projecting retaining flange on its outer periphery, the groove in said piston skirt being of such dimensions that only said retaining flange of said ring body is disposed in said groove in the piston skirt, said retaining flange being adapted to fit said groove and hold said spring ring body in position in the piston.

DEAN M. SOLENBERGER. 

